The couple, who have a six-month-old baby daughter together, as well as two children each from previous marriages, broke the news of their engagement in the Forthcoming Marriages section of the Times newspaper.

Ms Murdoch, who recently left her job as director of programmes and general manager at her father's company BSkyB to start her own television company and Mr Freud, son of former Liberal MP Sir Clement and a descendant of psychoanalyst Sigmund, are said to have August in mind as a possible date to tie the knot.

The announcement will put the Murdoch family under the spotlight for the second time this month following the revelation that Murdoch Snr is to have a new heir to his News Corporation empire, which includes the Times.

Speculation over the future of the family fortune was intensified after it emerged that his third wife, the Chinese-born Wendi Deng, is expecting their first child.

News that Murdoch, 70, is to become a father for the fifth time was broken by his Australian rivals, Fairfax Publications, in the Sydney Morning Herald while the couple were visiting the Cannes film festival.

The billionaire married Ms Deng two years ago following his divorce from his second wife, Anna, mother of his three younger children - Elisabeth, 32, Lachlan, 29, and James, 28. His first daughter, Prudence, lives in Britain with her husband and their three children.

The forthcoming marriage between Freud, a leading-celebrity spinner, and Murdoch, once named as one of Britain's highest profiled businesswomen, will seal a powerful partnership which began four years ago. The high-profile pair, dubbed the "golden couple" on the public relations and celebrity circuit, briefly split up earlier this year just three months after the birth of their baby girl Charlotte.